Self-fertilisation in Balanus improvisus Darwin

Abstract

Although hermaphroditism is universal in sessile barnacles, only a few species are known to be facultative self-fertilisers. This study tested the ability of Balanus improvisus Darwin to self-fertilise. Individuals were observed to carry well-developed ovaries and well-developed testes at the same time. Fertilisation took place and the eggs developed to larvae in both isolated and communal individuals. Self-fertilisation appears to take place somewhat later than cross-fertilisation. These laboratory results on self-fertilisation in B. improvisus are supported by field observations, in which isolated individuals were found with fertilised egg masses. B. improvisus can thus be added to the list of facultatively self-fertilising cirripedes. The ability to self-fertilise is especially advantageous for individuals of a species such as B. improvisus, which often has sparse and isolated populations. © 1990.